     (generic-equals [this other] Context [objects attributes incidence]))
   (hashCode [this]
     (hash-combine-hash Context objects attributes incidence)))
+
+(defn context?
+  "Returns true iff thing is a context."
+  [thing]
+  (instance? Context thing))
 
 (defmulti objects
   "Returns the objects of a formal context.."

  [(intersection (first concept) (objects subcontext)),
   (intersection (second concept) (attributes subcontext))])

;;;

nil

				     (I_2 [g_2,m_2]))])]
    (make-context-nc new-objs new-atts new-inz)))

;;; Subcontexts

(defn subcontext?
  "Tests whether ctx-1 is a subcontext ctx-2 or not."
